The project is not the subject. The project is not the thesis. Whether you are writing your dissertation, a journal article, or a book, the project is not simply the thesis. When I ask people about their projects the answer I get is always (or almost always) the subject of the project. Sometimes I ask specific questions like “what kind of project? Is it a dissertation? A thesis?” And still the answer I get is the subject of the project. But your project is not just about a subject; it has a certain form. It is a journal article, a dissertation, a book. It has a certain intention—to share a discovery, to support a position, to instruct others. It is aimed at a certain audience—peers, or students, or educated lay people.
If you can see that form, and understand how that form relates to the work you’re trying to accomplish, then the writing process becomes much easier: it’s less a shot in the dark, and more a purposeful action.